The present invention relates to a sample holding mechanism used for positioning and holding a sheet-like sample, and a sample working/observing apparatus that comprises the sample holding mechanism and performs working/observation upon the sample.
Up to this point, a photomask used in the manufacture of a liquid crystal flat panel display and the exposure process of semiconductor manufacture has been corrected by a focused ion beam apparatus and the like. In order to precisely work and observe a sample, such as the photomask, or a substrate patterned by the photomask, it is necessary to precisely position the sample inside the focused ion beam apparatus, and it is necessary to resolve the problems associated with an expansion and a contraction due to a temperature change inside or outside of the apparatus. In order to cope with the problems, an exposure apparatus for patterning a substrate or the sample is proposed which has means for raising the atmospheric temperature in a pre-alignment chamber which is provided along a path along which the sample is carried from the outside into the apparatus (e.g., JP-A-2005-32906). In such an exposure apparatus, it is possible to raise the temperature of the substrate in the pre-alignment chamber, using the temperature raising means, during a process for pre-aligning the substrate. Therefore, when evacuating the apparatus, even if the temperature of the substrate changes due to an adiabatic expansion of a gas, it is possible to adjust the temperature of the substrate to the outside air temperature and thereby prevent a distortion of the substrate. Further, it is unnecessary to provide a separate process for the temperature adjustment.
However, in such a case where same-sized samples are carried, it is possible to directly carry the samples by a standardized carrying system as mentioned above. However, in order to carry samples of various sizes, it is necessary to hold them with a sample holder so that the samples will be carried under the same carrying condition. Further, when a sheet-like sample such as a photomask is carried between the outside and the inside of the apparatus, to prevent a flexure of the sample and precisely position the sample, it is necessary to carry the sample while being held by the sample holder. Since the sample holder is formed, e.g., by a metal material or the like, whose rigidity is high, due to the necessity that the sample holder holds the sample, its thermal expansion coefficient is high in comparison with the sample, so that the distortion caused by the temperature change is large. Further, since the heat capacity is large, time is required for the sample holder to become thermally equilibratory with the ambient temperature environment. Therefore, like JP-A-2005-32906, even if the temperature adjustment was made only during the process for pre-aligning, the high heat capacity sample holder cannot be thermally equilibrated. That is, inside the apparatus, the sample holder expands or contracts due to the temperature change and thus the position of the sample held by the sample holder changes (drifts), so that it becomes impossible to perform the precise working and observation.
This invention has been made in view of the above-mentioned problems, and provides a sample holding mechanism which, even if it expands or contracts due to temperature changes, can hold the sample in place to thereby precisely position and hold the sample, and also provides a sample working/observing apparatus having this sample holding mechanism.